In the fields of medical imaging and security screening, non-invasive imaging techniques have gained importance due to benefits that include unobtrusiveness, convenience, and speed. In medical and research contexts, non-invasive imaging techniques are used to image organs or tissues beneath the surface of the skin. Similarly, in industrial or quality control (QC) contexts, non-invasive imaging techniques are used to examine parts or items for hidden defects that may not be evident from an external examination. In security screening, non-invasive imaging techniques are typically used to examine the contents of containers (e.g., packages, bags, or luggage) without opening the containers and/or to screen individuals entering or leaving a secure location.
A number of non-invasive imaging modalities exist today. One such technique, dual energy (DE) radiography, involves the acquisition of two X-ray images at different energies within a relatively small time interval. The two images are then used to decompose the imaged anatomy and create a first image of a first material (e.g., water) and a second image of a second material (e.g., iodine). While such materially decomposed images contain clinically pertinent information, they typically result in a lower signal to noise ratio (SNR) than conventional computed tomography images.
Existing techniques that attempt to increase the signal in such images are often accompanied by undesired radiation dosages. Accordingly, a variety of techniques have been developed that attempt to reduce the noise in the reconstructed images. However, such techniques have fallen short of reducing the noise to acceptable levels. In addition, many noise reduction techniques eliminate noise while introducing undesirable artifacts that contaminate the materially decomposed images. One problem noted with current DE image reconstruction methods is cross contamination (CC). In a cross-contaminated image, some parts of a first material can be represented as a second material and some parts of a second material can be represented as a first material. Accordingly, techniques are needed to overcome the problems associated with DE image reconstruction. The techniques described herein are intended to address one or more of these problems associated with DE imaging systems.
In medical imaging it is common to use a contrast agent for visualization of various body tissues. A contrast agent is a substance used to enhance contrast of some structures or fluids within a body subject to medical imaging. Iodine based contrast agents are commonly used.